Acknowledgement feedback in unlicensed new radio

ABSTRACT

Methods, systems, and devices for wireless communications are described. A user equipment (UE) and a base station may communicate in an unlicensed spectrum (e.g., a shared radio frequency spectrum band). As such, the UE may determine a codebook size for transmitting hybrid access request (HARQ) acknowledgement (ACK) feedback with respect to the unlicensed spectrum. Accordingly, the UE may base the HARQ ACK codebook size on a number of HARQ processes with which the UE has been configured. Additionally or alternatively, the UE may base the HARQ ACK codebook size on a number and/or duration of downlink channel monitoring occasions indicated by the base station. In some cases, the UE may base the HARQ ACK codebook size on a combination of the techniques described herein.

CROSS REFERENCES

The present application for patent claims the benefit of U.S.Provisional Patent Application No. 62/648,852 by ZHANG et al., entitled“Acknowledgement Feedback in Unlicensed New Radio,” filed Mar. 27, 2018,assigned to the assignee hereof, and which is expressly incorporated byreference herein.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to acknowledgement (ACK) feedback in unlicensed New Radio(NR).

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as NR systems. These systems may employ technologies such ascode division multiple access (CDMA), time division multiple access(TDMA), frequency division multiple access (FDMA), orthogonal frequencydivision multiple access (OFDMA), or discrete Fouriertransform-spread-OFDM (DFT-S-OFDM). A wireless multiple-accesscommunications system may include a number of base stations or networkaccess nodes, each simultaneously supporting communication for multiplecommunication devices, which may be otherwise known as user equipment(UE).

Some wireless communications systems may support ACK feedback toindicate if a wireless device (e.g., a UE) successfully decodes downlinkmessages (i.e., data transmissions) where the downlink message decodingis based on one or more detected downlink control messages (e.g., adownlink grant or downlink control information (DCI)). Accordingly, thewireless device may determine an ACK codebook size for transmitting theACK feedback, where the ACK codebook size may be based on the number ofdownlink messages included in the ACK feedback, a static or dynamicconfiguration for the ACK feedback, etc. In deployments supportingunlicensed spectrums (e.g., unlicensed NR), one or more downlinkmessages may not be received correctly and the wireless device maydetermine an ACK codebook size that is incorrect or inefficient fortransmitting the ACK feedback.

SUMMARY

The described techniques relate to improved methods, systems, devices,or apparatuses that support acknowledgement (ACK) feedback in unlicensedNew Radio (NR). Generally, the described techniques provide a userequipment (UE) with means to determine a hybrid access request (HARQ)ACK codebook size for transmitting HARQ feedback based on a duration ofone or more downlink channel monitoring occasions, a number ofconfigured HARQ processes, or a combination thereof. Additionally oralternatively, the HARQ codebook size may further be based on a numberof downlink channel monitoring occasions, a set of downlink channelmonitoring occasions, a total number of channels associated with the UE,a channel indication of the total number of channels, or a combinationthereof. In some cases, the UE may receive a feedback trigger and thendetermine the HARQ ACK codebook size after receiving the feedbacktrigger. Additionally, the UE may populate the HARQ feedback based on anACK delay indication, where the HARQ feedback may be populated usingdecoding results and/or default values based on the ACK delay. It is tobe noted that various elements detailed as follows may be combinedbetween independent claims described herein.

A method of wireless communication in a shared radio frequency spectrumband is described. The method may include receiving, at the UE, adownlink grant scheduling a downlink channel to be received by the UE,and identifying, in association with the downlink grant, an ACK delayindication, where the ACK delay indication indicates a minimum time bywhich hybrid access request (HARQ) feedback is to be delayed afterreceiving the downlink channel. The method may also include receiving,at the UE, the downlink channel, determining whether to transmit HARQfeedback for the downlink channel based on a value of the ACK delay, andtransmitting the HARQ feedback based on the determining.

An apparatus for wireless communication in a shared radio frequencyspectrum band is described. The apparatus may include a processor,memory in electronic communication with the processor, and instructionsstored in the memory. The instructions may be executable by theprocessor to cause the apparatus to receive, at the UE, a downlink grantscheduling a downlink channel to be received by the UE, and identify, inassociation with the downlink grant, an ACK delay indication, where theACK delay indication indicates a minimum time by which hybrid accessrequest (HARQ) feedback is to be delayed after receiving the downlinkchannel. The instructions may also be executable by the processor tocause the apparatus to receive, at the UE, the downlink channel,determine whether to transmit HARQ feedback for the downlink channelbased on a value of the ACK delay indication, and transmit the HARQfeedback based on the determining.

Another apparatus for wireless communication in a shared radio frequencyspectrum band is described. The apparatus may include means forreceiving, at the UE, a downlink grant scheduling a downlink channel tobe received by the UE, and identifying, in association with the downlinkgrant, an ACK delay indication, where the ACK delay indication indicatesa minimum time by which hybrid access request (HARQ) feedback is to bedelayed after receiving the downlink channel. The apparatus may alsoinclude means for receiving, at the UE, the downlink channel,determining whether to transmit HARQ feedback for the downlink channelbased on a value of the ACK delay indication, and transmitting the HARQfeedback based on the determining.

A non-transitory computer-readable medium storing code for wirelesscommunication in a shared radio frequency spectrum band is described.The code may include instructions executable by a processor to receive,at the UE, a downlink grant scheduling a downlink channel to be receivedby the UE, and identify, in association with the downlink grant, an ACKdelay indication, where the ACK delay indication indicates a minimumtime by which hybrid access request (HARQ) feedback is to be delayedafter receiving the downlink channel. The code may also includeinstructions executable by a processor to receive, at the UE, thedownlink channel, determine whether to transmit HARQ feedback for thedownlink channel based on a value of the ACK delay indication, andtransmit the HARQ feedback based on the determining.

A method of wireless communication in a shared radio frequency spectrumband is described. The method may include receiving, in a downlinkcontrol information message, a channel indication for a number ofchannels to be included in determining a hybrid access request (HARQ)ACK codebook size, determining the HARQ ACK codebook size based on thenumber of channels indicated by the channel indication, and transmittingHARQ feedback in accordance with the HARQ ACK codebook size.

An apparatus for wireless communication in a shared radio frequencyspectrum band is described. The apparatus may include a processor,memory in electronic communication with the processor, and instructionsstored in the memory. The instructions may be executable by theprocessor to cause the apparatus to receive, in a downlink controlinformation message, a channel indication for a number of channels to beincluded in determining a hybrid access request (HARQ) ACK codebooksize, determine the HARQ ACK codebook size based on the number ofchannels indicated by the channel indication, and transmit HARQ feedbackin accordance with the HARQ ACK codebook size.

Another apparatus for wireless communication in a shared radio frequencyspectrum band is described. The apparatus may include means forreceiving, in a downlink control information message, a channelindication for a number of channels to be included in determining ahybrid access request (HARQ) ACK codebook size, determining the HARQ ACKcodebook size based on the number of channels indicated by the channelindication, and transmitting HARQ feedback in accordance with the HARQACK codebook size.

A non-transitory computer-readable medium storing code for wirelesscommunication in a shared radio frequency spectrum band is described.The code may include instructions executable by a processor to receive,in a downlink control information message, a channel indication for anumber of channels to be included in determining a hybrid access request(HARQ) ACK codebook size, determine the HARQ ACK codebook size based onthe number of channels indicated by the channel indication, and transmitHARQ feedback in accordance with the HARQ ACK codebook size.

A method of wireless communication in a shared radio frequency spectrumband is described. The method may include identifying at least onedownlink channel monitoring occasion, receiving, at the UE, a feedbacktrigger for transmission of HARQ feedback, determining a HARQ ACKcodebook size based on a number of configured HARQ processes, on thedownlink channel monitoring occasions, or a combination thereof, andtransmitting the HARQ feedback in accordance with the HARQ ACK codebooksize.

An apparatus for wireless communication in a shared radio frequencyspectrum band is described. The apparatus may include a processor,memory in electronic communication with the processor, and instructionsstored in the memory. The instructions may be executable by theprocessor to cause the apparatus to identify at least one downlinkchannel monitoring occasion, receive, at the UE, a feedback trigger fortransmission of HARQ feedback, determine a HARQ ACK codebook size basedon a number of configured HARQ processes, on the downlink channelmonitoring occasions, or a combination thereof, and transmit the HARQfeedback in accordance with the HARQ ACK codebook size.

Another apparatus for wireless communication in a shared radio frequencyspectrum band is described. The apparatus may include means foridentifying at least one downlink channel monitoring occasion,receiving, at the UE, a feedback trigger for transmission of HARQfeedback, determining a HARQ ACK codebook size based on a number ofconfigured HARQ processes, on the downlink channel monitoring occasions,or a combination thereof, and transmitting the HARQ feedback inaccordance with the HARQ ACK codebook size.

A non-transitory computer-readable medium storing code for wirelesscommunication in a shared radio frequency spectrum band is described.The code may include instructions executable by a processor to identifyat least one downlink channel monitoring occasion, receive, at the UE, afeedback trigger for transmission of HARQ feedback, determine a HARQ ACKcodebook size based on a number of configured HARQ processes, on thedownlink channel monitoring occasions, or a combination thereof, andtransmit the HARQ feedback in accordance with the HARQ ACK codebooksize.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationthat supports acknowledgement (ACK) feedback in unlicensed New Radio(NR) in accordance with aspects of the present disclosure.

FIGS. 2A, 2B, and 2C illustrate examples of ACK feedback timelines thatsupport ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure.

FIG. 3 illustrates an example of a wireless communications system thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure.

FIGS. 4 and 5 illustrate examples of ACK feedback schedules inunlicensed NR in accordance with aspects of the present disclosure.

FIG. 6 illustrates an example of a downlink monitoring scheme thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure.

FIG. 7 illustrates an example of an adjusted ACK feedback schedule thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure.

FIG. 8 illustrates an example of an ACK feedback scheme that supportsACK feedback in unlicensed NR in accordance with aspects of the presentdisclosure.

FIG. 9 illustrates an example of a process flow that supports ACKfeedback in unlicensed NR in accordance with aspects of the presentdisclosure.

FIGS. 10 through 12 show block diagrams of a device that supports ACKfeedback in unlicensed NR in accordance with aspects of the presentdisclosure.

FIG. 13 illustrates a block diagram of a system including a userequipment (UE) that supports ACK feedback in unlicensed NR in accordancewith aspects of the present disclosure.

FIGS. 14 through 16 show block diagrams of a device that supports ACKfeedback in unlicensed NR in accordance with aspects of the presentdisclosure.

FIG. 17 illustrates a block diagram of a system including a base stationthat supports ACK feedback in unlicensed NR in accordance with aspectsof the present disclosure.

FIGS. 18 through 20 illustrate methods for ACK feedback in unlicensed NRin accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

In some wireless communications systems (e.g., New Radio (NR)), a userequipment (UE) may utilize a hybrid access request (HARQ)acknowledgement (ACK) feedback scheme to indicate if one or moredownlink data messages (e.g., physical downlink shared channel (PDSCH)messages) have been successfully received and decoded from a basestation after receiving one or more downlink control messages (e.g.,physical downlink control channel (PDCCH) messages). Accordingly, the UEmay determine a HARQ ACK codebook size for transmitting the HARQ ACKfeedback, where the HARQ ACK codebook may indicate a payload size forthe HARQ ACK feedback in addition to how to populate the payload. Forexample, the HARQ ACK codebook may indicate that the HARQ ACK feedbackincludes feedback for a number of downlink data messages and/or HARQprocesses with a corresponding size (e.g., number of bits) fortransmitting the HARQ ACK feedback.

In some cases, the ACK codebook size may be based in part on asemi-static or dynamic configuration. Accordingly, the base station mayindicate a semi-static configuration for the HARQ ACK feedback inprevious signaling (e.g., a radio resource control (RRC) configuration),where the HARQ ACK feedback is based on maximum and minimum slot timingvalues. The slot timing values may indicate a number of slots that theUE reports HARQ ACK feedback for downlink data messages included in thecorresponding slots. For example, the UE may transmit HARQ ACK feedbackfor downlink data messages in slots extending from the minimum indicatedslot to the maximum indicated slot. Alternatively, the base station mayindicate a dynamic configuration for the HARQ ACK feedback based ondetected downlink messages (e.g., downlink control information (DCI)).As such, the base station may indicate one or more occasions that the UEmonitors for the downlink messages. When the UE detects a downlinkmessage triggering the HARQ ACK feedback, the UE may transmit the HARQACK feedback starting from a slot corresponding to the detected downlinkmessage up to a last received downlink message. In one example of adynamic ACK codebook determination, downlink control messages mayinclude an indication of an ACK resource to be used corresponding to anumber of data transmissions. Accordingly, the UE may determine an ACKcodebook size for an ACK resource dynamically based on all downlinkcontrol messages that point to the ACK resource.

In some cases, the wireless communications system may further supportcommunications in an unlicensed spectrum (e.g., a shared radio frequencyspectrum band), licensed spectrum, or a combination of licensed andunlicensed spectrums. As such, the UE may determine an inefficient ACKcodebook size for transmitting the HARQ ACK feedback. For example,techniques associated with the unlicensed spectrum (e.g.,listen-before-talk (LBT)) may add to a delay time for transmitting theHARQ ACK feedback or may forego the scheduled HARQ ACK feedbacktransmission opportunity due to LBT failure. The HARQ ACK feedback maynot be received at the base station due to unforeseen interference, oneor more processes associated with the HARQ may not be appropriatelyreceived and/or decoded, or the HARQ ACK feedback may span more than onetransmission opportunities (TxOps) associated with the unlicensedspectrum. Accordingly, the HARQ ACK feedback may not include feedbackfor one or more of the missed HARQ processes (e.g., due to interference,processing times that extend past the end of a TxOp, etc.), and the UEmay determine an ACK codebook size that does not fully capture the HARQACK feedback. As such, it may be desirable to have mechanisms such as,for example, re-triggering HARQ ACK feedback at additional instances.

To determine an appropriate codebook size, the UE may base the ACKcodebook size on a number of HARQ processes with which the UE has beenconfigured. When the HARQ ACK feedback is triggered, the UE may transmitfeedback for all of the HARQ processes. The base station may trigger theHARQ ACK feedback embedded in the downlink message (e.g., downlink oruplink grant) or in a separate downlink message (e.g., a separate DCI).If the ACK feedback for a particular HARQ process is ready when thetrigger is received, the UE may transmit appropriate ACK feedback basedon decoding results. Alternatively, if the ACK feedback for a particularHARQ process is not ready when the trigger is received (e.g., based onan associated ACK delay time), the UE may transmit a previous value or adefault value (e.g., a negative acknowledgement (NACK)) for theparticular HARQ process. In some cases, the UE may transmit the HARQ ACKfeedback once per TxOp or may transmit faster the HARQ ACK feedbackfaster (e.g., every slot).

Additionally or alternatively, the UE may base the ACK codebook size onmonitoring occasions for downlink messages (e.g., a number and/orduration of the monitoring occasions where the UE monitors for adownlink grant in predetermined slots for the monitoring occasions). Forexample, a control channel may be used to carry information to decodedata and the ACK codebook may be a function of when the controlinformation may potentially show up in the monitoring occasions. Assuch, the ACK codebook size may include ACK feedback for parts of one ormore TxOps. For example, the UE may need time to process a downlinkmessage (i.e., a downlink data transmission, PDSCH message, etc.) thatextends past the end of a first TxOp. The UE may transmit ACK feedbackfor the downlink message with the ACK codebook size in a subsequent TxOpwhile skipping a gap where the base station does not have medium accessin the unlicensed spectrum. Additionally, if the UE misses one or moreACK transmissions due to issues associated with the unlicensed spectrum(e.g., LBT and/or interference), the base station may request subsequentACK feedback to include the missed ACK transmission(s).

In some cases, the UE may base the ACK codebook size on a combination ofthe techniques described herein. For example, the base station mayindicate one or more monitoring occasions for the UE to utilize formonitoring downlink control information or other data (e.g., DCI) forACK feedback on the corresponding downlink data transmission within oneTxOp. Additionally, if the ACK feedback extends into a second TxOp, thebase station may trigger (e.g., in a downlink or uplink grant orseparate DCI) the UE to transmit ACK feedback for a number (or a subset)of configured HARQ processes for the UE. As such, the UE may determinethe ACK codebook size accordingly based on the type of ACK feedbackindicated by the base station. Additionally or alternatively, the UE maybase the ACK codebook size on a number of channels the UE is configuredto communicate on. The number of channels may be based on a number ofchannels indicated for the UE (e.g., active channels or a subsetthereof).

Aspects of the disclosure are initially described in the context ofwireless communications systems. Additional aspects of the disclosureare then described with respect to ACK feedback schedules and schemes,monitoring schemes, and a process flow. Aspects of the disclosure arefurther illustrated by and described with reference to apparatusdiagrams, system diagrams, and flowcharts that relate to ACK feedback inunlicensed NR.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A)network, an LTE-A Pro network, or a NR network. In some cases, wirelesscommunications system 100 may support enhanced broadband communications,ultra-reliable (e.g., mission critical) communications, low latencycommunications, or communications with low-cost and low-complexitydevices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation Node B orgiga-nodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up only a portion of the geographic coverage area110, and each sector may be associated with a cell. For example, eachbase station 105 may provide communication coverage for a macro cell, asmall cell, a hot spot, or other types of cells, or various combinationsthereof. In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap, and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may be a personal electronicdevice such as a cellular phone, a personal digital assistant (PDA), atablet computer, a laptop computer, or a personal computer. In someexamples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples half-duplexcommunications may be performed at a reduced peak rate. Other powerconservation techniques for UEs 115 include entering a power saving“deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105, or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1 or otherinterface). Base stations 105 may communicate with one another overbackhaul links 134 (e.g., via an X2 or other interface) either directly(e.g., directly between base stations 105) or indirectly (e.g., via corenetwork 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 MHz to 300 GHz.Generally, the region from 300 MHz to 3 GHz is known as the ultra-highfrequency (UHF) region or decimeter band, since the wavelengths rangefrom approximately one decimeter to one meter in length. UHF waves maybe blocked or redirected by buildings and environmental features.However, the waves may penetrate structures sufficiently for a macrocell to provide service to UEs 115 located indoors. Transmission of UHFwaves may be associated with smaller antennas and shorter range (e.g.,less than 100 km) compared to transmission using the smaller frequenciesand longer waves of the high frequency (HF) or very high frequency (VHF)portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that can tolerate interference from otherusers.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize licensedradio frequency spectrum bands, unlicensed radio frequency spectrumbands, or a combination of licensed and unlicensed radio frequencyspectrum bands. For example, wireless communications system 100 mayemploy License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radioaccess technology, or NR technology in an unlicensed band such as the 5GHz ISM band. When operating in unlicensed radio frequency spectrumbands, wireless devices such as base stations 105 and UEs 115 may employLBT procedures to ensure a frequency channel is clear beforetransmitting data. In some cases, operations in unlicensed bands may bebased on a CA configuration in conjunction with CCs operating in alicensed band (e.g., LAA). Operations in unlicensed spectrum may includedownlink transmissions, uplink transmissions, peer-to-peertransmissions, or a combination of these. Duplexing in unlicensedspectrum may be based on frequency division duplexing (FDD), timedivision duplexing (TDD), or a combination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving devices are equipped with one ormore antennas. MIMO communications may employ multipath signalpropagation to increase the spectral efficiency by transmitting orreceiving multiple signals via different spatial layers, which may bereferred to as spatial multiplexing. The multiple signals may, forexample, be transmitted by the transmitting device via differentantennas or different combinations of antennas. Likewise, the multiplesignals may be received by the receiving device via different antennasor different combinations of antennas. Each of the multiple signals maybe referred to as a separate spatial stream, and may carry bitsassociated with the same data stream (e.g., the same codeword) ordifferent data streams. Different spatial layers may be associated withdifferent antenna ports used for channel measurement and reporting. MIMOtechniques include single-user MIMO (SU-MIMO) where multiple spatiallayers are transmitted to the same receiving device, and multiple-userMIMO (MU-MIMO) where multiple spatial layers are transmitted to multipledevices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g., synchronizationsignals, reference signals, beam selection signals, or other controlsignals) may be transmitted by a base station 105 multiple times indifferent directions, which may include a signal being transmittedaccording to different beamforming weight sets associated with differentdirections of transmission. Transmissions in different beam directionsmay be used to identify (e.g., by the base station 105 or a receivingdevice, such as a UE 115) a beam direction for subsequent transmissionand/or reception by the base station 105. Some signals, such as datasignals associated with a particular receiving device, may betransmitted by a base station 105 in a single beam direction (e.g., adirection associated with the receiving device, such as a UE 115). Insome examples, the beam direction associated with transmissions along asingle beam direction may be determined based at least in part on asignal that was transmitted in different beam directions. For example, aUE 115 may receive one or more of the signals transmitted by the basestation 105 in different directions, and the UE 115 may report to thebase station 105 an indication of the signal it received with a highestsignal quality, or an otherwise acceptable signal quality. Althoughthese techniques are described with reference to signals transmitted inone or more directions by a base station 105, a UE 115 may employsimilar techniques for transmitting signals multiple times in differentdirections (e.g., for identifying a beam direction for subsequenttransmission or reception by the UE 115), or transmitting a signal in asingle direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., a UE 115, which may be an example of a mmWreceiving device) may try multiple receive beams when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets applied to signals receivedat a plurality of antenna elements of an antenna array, or by processingreceived signals according to different receive beamforming weight setsapplied to signals received at a plurality of antenna elements of anantenna array, any of which may be referred to as “listening” accordingto different receive beams or receive directions. In some examples areceiving device may use a single receive beam to receive along a singlebeam direction (e.g., when receiving a data signal). The single receivebeam may be aligned in a beam direction determined based on listeningaccording to different receive beam directions (e.g., a beam directiondetermined to have a highest signal strength, highest signal-to-noiseratio, or otherwise acceptable signal quality based on listeningaccording to multiple beam directions).

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays, which may support MIMOoperations, or transmit or receive beamforming. For example, one or morebase station antennas or antenna arrays may be co-located at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may have an antenna array witha number of rows and columns of antenna ports that the base station 105may use to support beamforming of communications with a UE 115.Likewise, a UE 115 may have one or more antenna arrays that may supportvarious MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-basednetwork that operate according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may insome cases perform packet segmentation and reassembly to communicateover logical channels. A Medium Access Control (MAC) layer may performpriority handling and multiplexing of logical channels into transportchannels. The MAC layer may also use HARQ to provide retransmission atthe MAC layer to improve link efficiency. In the control plane, theRadio Resource Control (RRC) protocol layer may provide establishment,configuration, and maintenance of an RRC connection between a UE 115 anda base station 105 or core network 130 supporting radio bearers for userplane data. At the Physical (PHY) layer, transport channels may bemapped to physical channels.

In some cases, UEs 115 and base stations 105 may support retransmissionsof data to increase the likelihood that data is received successfully.HARQ feedback is one technique of increasing the likelihood that data isreceived correctly over a communication link 125. HARQ may include acombination of error detection (e.g., using a cyclic redundancy check(CRC)), forward error correction (FEC), and retransmission (e.g.,automatic repeat request (ARQ)). HARQ may improve throughput at the MAClayer in poor radio conditions (e.g., signal-to-noise conditions). Insome cases, a wireless device may support same-slot HARQ feedback, wherethe device may provide HARQ feedback in a specific slot for datareceived in a previous symbol in the slot. In other cases, the devicemay provide HARQ feedback in a subsequent slot, or according to someother time interval.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period of T_(s)=1/30,720,000 seconds. Time intervals of a communications resource may beorganized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100, andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriersusing sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an E-UTRA absolute radiofrequency channel number (EARFCN)), and may be positioned according to achannel raster for discovery by UEs 115. Carriers may be downlink oruplink (e.g., in an FDD mode), or be configured to carry downlink anduplink communications (e.g., in a TDD mode). In some examples, signalwaveforms transmitted over a carrier may be made up of multiplesub-carriers (e.g., using multi-carrier modulation (MCM) techniques suchas OFDM or DFT-s-OFDM).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR,etc.). For example, communications over a carrier may be organizedaccording to TTIs or slots, each of which may include user data as wellas control information or signaling to support decoding the user data. Acarrier may also include dedicated acquisition signaling (e.g.,synchronization signals or system information, etc.) and controlsignaling that coordinates operation for the carrier. In some examples(e.g., in a carrier aggregation configuration), a carrier may also haveacquisition signaling or control signaling that coordinates operationsfor other carriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or RBs) within a carrier (e.g., “in-band” deployment of anarrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations105 or UEs 115) may have a hardware configuration that supportscommunications over a particular carrier bandwidth, or may beconfigurable to support communications over one of a set of carrierbandwidths. In some examples, the wireless communications system 100 mayinclude base stations 105 and/or UEs that can support simultaneouscommunications via carriers associated with more than one differentcarrier bandwidth.

Wireless communications system 100 may support communication with a UE115 on multiple cells or carriers, a feature which may be referred to ascarrier aggregation (CA) or multi-carrier operation. A UE 115 may beconfigured with multiple downlink CCs and one or more uplink CCsaccording to a carrier aggregation configuration. Carrier aggregationmay be used with both FDD and TDD component carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider carrier or frequency channel bandwidth, shortersymbol duration, shorter TTI duration, or modified control channelconfiguration. In some cases, an eCC may be associated with a carrieraggregation configuration or a dual connectivity configuration (e.g.,when multiple serving cells have a suboptimal or non-ideal backhaullink). An eCC may also be configured for use in unlicensed spectrum orshared spectrum (e.g., where more than one operator is allowed to usethe spectrum). An eCC characterized by wide carrier bandwidth mayinclude one or more segments that may be utilized by UEs 115 that arenot capable of monitoring the whole carrier bandwidth or are otherwiseconfigured to use a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration may beassociated with increased spacing between adjacent subcarriers. Adevice, such as a UE 115 or base station 105, utilizing eCCs maytransmit wideband signals (e.g., according to frequency channel orcarrier bandwidths of 20, 40, 60, 80 MHz, etc.) at reduced symboldurations (e.g., 16.67 microseconds). A TTI in eCC may consist of one ormultiple symbol periods. In some cases, the TTI duration (e.g., thenumber of symbol periods in a TTI) may be variable.

Wireless communications systems such as an NR system may utilize anycombination of licensed, shared, unlicensed spectrum bands, or acombination of the different spectrum bands, among others. Theflexibility of eCC symbol duration and subcarrier spacing may allow forthe use of eCC across multiple spectrums. In some examples, NR sharedspectrum may increase spectrum utilization and spectral efficiency,specifically through dynamic vertical (e.g., across frequency) andhorizontal (e.g., across time) sharing of resources.

As described herein, HARQ feedback may be utilized to increase thelikelihood that data is received correctly over a communication link125. In some cases, the HARQ feedback may include an indication ofwhether the data is received correctly, where a UE 115 may transmit anACK/NACK message to a base station 105 based on a successful detectionand decoding of an amount of the data (e.g., ACK if successful, NACK ifunsuccessful). Further, the UE 115 may transmit this ACK feedbackaccording to a HARQ ACK codebook size (e.g., ACK/NACK payload size andhow to populate the ACK/NACK payload), where the HARQ ACK codebook sizeis based in part on a semi-static or dynamic configuration for the ACKfeedback, which may indicate an amount of data to be represented by theACK feedback (e.g., a number of downlink messages). The base station 105may indicate the configuration to the UE 115 via high layer signaling(e.g., RRC).

FIGS. 2A, 2B, and 2C illustrate examples of ACK feedback timelines 200,201, and 202, respectively, that support ACK feedback in unlicensed NRin accordance with various aspects of the present disclosure. In someexamples, ACK feedback timelines 200, 201, and 202 may implement aspectsof wireless communication system 100. A UE 115 may receive one or moredownlink data transmissions (e.g., PDSCH) and/or downlink controltransmissions (e.g., PDCCH) from a base station 105 and transmit ACKfeedback for the one or more downlink transmissions in an uplinktransmission (e.g., physical uplink control channel (PUCCH)) to the basestation 105, where the UE 115 and the base station 105 may be examplesof corresponding devices as described with reference to FIG. 1. In somecases, the UE 115 may, for example, transmit the ACK feedback inaccordance with a HARQ ACK codebook size, as described herein, where theHARQ ACK codebook size may be based on a semi-static or dynamicconfiguration.

In ACK feedback timeline 200, when the UE 115 is configured with asemi-static HARQ ACK codebook size, the UE 115 may determine a number(M) of downlink control channel (e.g., PDCCH) monitoring occasion(s) forthe downlink control channel based on maximum and minimum slot timingvalues provided to the UE 115 by the base station 105, where the maximumand minimum slot timing values may be based on processing time for ACKfeedback for the UE 115 (e.g., included in a UE capability report to thebase station 105). For example, the base station may indicate downlinkchannel monitoring occasions (e.g., downlink control channel monitoringoccasions and/or downlink data channel monitoring occasions) for the UE115 in each slot of a frame. Accordingly, the UE 115 may then transmit acorresponding HARQ ACK codebook in a same PUCCH based on the monitoringoccasions extending from the minimum slot time up to the maximum slottime. For example, as shown, for a minimum slot timing value of one (1)and a maximum slot timing value of seven (7) and monitoring occasions ineach slot, the UE 115 may transmit ACK feedback according to a HARQ ACKcodebook for slots zero (0) to six (6) in slot seven (7) after receivinga trigger for the ACK feedback in slot six (6).

Alternatively, in ACK feedback timeline 201, for a semi-static HARQ ACKcodebook size and a minimum slot timing value of one (1) and a maximumslot timing value of seven (7) and monitoring occasions in each evennumbered slot, the UE 115 may transmit ACK feedback according to a HARQACK codebook for the even numbered slots up to six (e.g., slots 0, 2, 4,and 6) in slot seven (7) after receiving a trigger (e.g., a downlinkgrant) for the ACK feedback in slot six (6). If no trigger is received,the UE 115 may not transmit ACK feedback for the one or more slots.Accordingly, the ACK codebook may be a function of M in this case. Eachtime the UE 115 receives a downlink grant (e.g., the trigger), the UE115 may report the ACK feedback based on the above description, unlessthe UE 115 does not receive a downlink grant.

The determination for M may be based on a monitoring periodicity for thedownlink control channel, a monitoring offset for the downlink controlchannel, and a monitoring pattern for the downlink control channelwithin a slot for each control resource set in a set of control resourcesets configured to the UE 115. For a serving cell (e.g., cell in thebase station 105) and for a HARQ ACK codebook determination, thedownlink channel monitoring occasions may be indexed in an ascendingorder in time. Additionally, for a given downlink channel monitoringoccasion, the UE 115 may determine ACK feedback for all serving cells.

In some cases, the ACK feedback sent on uplink may include the ACKfeedback for all slots within the codebook size determination window.However, in other cases, each DCI may include a pointer to an ACKresource (e.g., an ACK resource indicator). The ACK codebook size maystill be based on all slots that are may be included within the codebooksize determination window (which may include DCI that point to the ACKresources, other slots that may not have DCI detected, or slots that mayhave DCI pointed to another ACK resource). The ACK feedback for slotswhose DCI points to the ACK resource may be set per PDSCH decodingstatus, while ACK feedback for rest of the slots may be set to a fixedvalue such as in NACK. Enhancements to the HARQ feedback process mayallow the UE 115 to switch between the above two methods of HARQ ACKfeedback based on for example, an explicit indication in the DCI or animplicit indication based on some other parameters in the DCI. Anexample of an implicit indication may include an indication that thevalue M for a codebook size determination is determined through the DCIin addition to an RRC configuration. In examples where the value M inthe DCI differs from the value for M configured through RRC, the UE 115may use an explicit indication. In further examples where the value M inthe DCI is the same as the value for M configured through RRC, the UE115 may use an implicit indication.

In some cases, an indication of carriers, a number of carriers, and awindow size for which the ACK feedback is requested may be jointly codedwith an ACK resource indicator (e.g., the pointer to an ACK resourceincluded in a DCI). The UE 115 may receive this joint coding based on ahigher number of bits for the ACK resource indicator or with a same bitsutilized for the ACK resource indicator. For example, a mapping may beperformed from the ACK resource indicator to both the ACK resource andthe window size, where the mapping is indicated to the UE 115 during anRRC configuration. Additionally or alternatively, the mapping may beimplicit. For example, a larger ACK resource (e.g., as indicated by theACK resource indicator) may correspond to a larger window size for theACK feedback.

Alternatively, in ACK feedback timeline 202, when the UE 115 isconfigured with a dynamic HARQ ACK codebook size, a value of a counterdownlink assignment indicator (DAI) field in a downlink message (e.g.,DCI) may denote an accumulative number (e.g., a total DAI) of servingcell/downlink channel monitoring occasion-pair(s) up to a currentserving cell and current downlink channel monitoring occasion, first inincreasing order of serving cell index and then in increasing order ofdownlink channel monitoring occasion index (m), where 0≤m<M. Thedownlink channel monitoring occasions may be either downlink datachannel monitoring occasions or downlink control channel monitoringoccasions. The UE 115 may determine the value of M to be similar to thesemi-static HARQ ACK codebook, except the maximum slot timing value maybe replaced by the slot timing value indicated in a first downlinkmessage the UE 115 detects, and the minimum slot timing value may bereplaced by the slot timing value indicated in a last downlink messagethe UE 115 detects and for which the UE 115 transmits ACK feedback in asame PUCCH. For example, for a minimum slot timing value of one (1) anda maximum slot timing value of seven (7) and monitoring occasions ineach even numbered slot, the first downlink message may be received inslot two (2). As such, the UE 115 may transmit ACK feedback for slots 2,4, and 6 after receiving a trigger (e.g., a downlink grant) for the ACKfeedback in slot six (6).

The value of the total DAI in the downlink messages (e.g., DCI) maydenote a total number of serving cell/downlink channel monitoringoccasion-pair(s) in which downlink shared channel (e.g., physicaldownlink shared channel (PDSCH)) reception(s) associated with thedownlink messages are present up to the current downlink channelmonitoring occasion m and may be updated from downlink channelmonitoring occasion to downlink channel monitoring occasion.Accordingly, the HARQ ACK codebook may be a function of M, the counterDAI, and the total DAI in this case. Additionally or alternatively, theHARQ ACK feedback size for a particular ACK resource may be based onDCIS that point to the ACK resource. In an example of HARQ feedback,DCIS on slots 1, 2, 4, and 6 may point to slots 7, 8, 7, and 7,respectively. The HARQ feedback on slot 7 would include HARQ feedbackfor DCIS received on slot 1, 4, and 6 while HARQ feedback on slot 8would include HARQ feedback for DCI on slot 2. In this example, thecounter DAI and total DAI indicated in the DCIS may be maintained andincremented separately for DCIS corresponding to ACK feedback in slots 7and 8, respectively.

The counter DAI may increase in accordance with a cell index, as well aswith the downlink channel monitoring occasion. Additionally oralternatively, the total DAI may denote the total number of servingcell/downlink channel monitoring occasion-pair(s) up to a currentserving cell and current downlink channel monitoring occasion. Forexample, in an exemplary case with two (2) serving cells and two (2)downlink channel monitoring occasions, on the first downlink channelmonitoring occasion, the downlink control channel (e.g., PDCCH) for afirst serving cell may indicate a counter DAI of one (1) and a total DAIof two (2) and the downlink control channel for a second serving cellmay indicate a counter DAI of two (2) and a total DAI of two (2). On thesecond PDCCH monitoring occasion, the downlink control channel for thefirst serving cell may indicate a counter DAI of three (3) and a totalDAI of four (4) and the downlink control channel for the second servingcell may indicate a counter DAI of four (4) and a total DAI of four (4).As such, the HARQ ACK codebook is a function of M, the counter DAI, andthe total DAI for each cell in each downlink channel monitoringoccasion.

In some cases, a wireless communications system may supportcommunications in an unlicensed spectrum (e.g., unlicensed NR or ashared radio frequency spectrum band), a licensed spectrum, or acombination of the unlicensed and licensed spectrums. As such, a UE 115may determine a HARQ ACK codebook size for transmitting the ACK feedbackwith respect to the unlicensed spectrum. For example, attempting tocommunicate in the unlicensed spectrum may lead to missed ACK feedbacktransmissions due to interference or LBT issues or due to a processingtime associated with the ACK feedback extending past the end of a TxOp(e.g., access to the unlicensed spectrum is no longer available until asubsequent TxOp occurs). Accordingly, the UE 115 may base the HARQ ACKcodebook size on a number of HARQ processes with which the UE 115 hasbeen configured. When the ACK feedback is triggered, the UE 115 maytransmit feedback for all of the HARQ processes, where the feedback mayinclude a previous value, a default value, or a new value based on whena processing time for the ACK feedback finishes compared to when thetrigger is received. Additionally or alternatively, the UE 115 may basethe ACK codebook size on downlink channel monitoring occasions. In somecases, the UE 115 may base the ACK codebook size on a combination of thetechniques described herein.

FIG. 3 illustrates an example of a wireless communications system 300that supports ACK feedback in unlicensed NR in accordance with variousaspects of the present disclosure. In some examples, wirelesscommunications system 300 may implement aspects of wirelesscommunication system 100. Wireless communications system 300 may includea base station 105-a and a UE 115-a, which may be examples ofcorresponding base stations 105 and UEs 115 as described with referenceto FIGS. 1 and 2.

As described herein, base station 105-a and UE 115-a may communicate inan unlicensed spectrum (e.g., a shared radio frequency spectrum band)and may employ HARQ ACK feedback techniques to indicate whether data hasbeen received correctly at UE 115-a. For example, base station 105-a maytransmit one or more downlink messages to UE 115-a on resources of acarrier 305. Accordingly, UE 115-a may transmit an indication of whetherthe one or more downlink messages were received and decoded correctly onresources of a carrier 310. In some cases, carriers 305 and 310 may bethe same carrier. Additionally, base station 105-a may transmit an ACKtrigger 315 on carrier 305, where UE 115-a responds with ACK feedback320 on carrier 310. ACK trigger 315 may be included in a downlink oruplink grant (e.g., downlink message such as PDCCH), or UE 115-a may beexplicitly triggered to transmit ACK feedback 320 (e.g., in a separateDCI message).

In some cases, ACK trigger 315 may be jointly coded with a delay field(e.g., a time between receiving a downlink message and ACK feedback 320should be ready from UE 115-a). As such, a value for the delay field mayindicate ACK trigger 315 is not present (e.g., delay field value equalszero (0), a largest delay value, or some other reserved delay value)when zero delay is not supported by UE 115-a or that a feedback timeassociated with the value is beyond the end of a current TxOp. When ACKtrigger 315 is present, UE 115-a may be indicated, by base station105-a, to report ACK feedback 320 based on one or more downlink channelmonitoring occasions (e.g., a duration and/or number of downlink datachannel monitoring occasions or downlink control channel monitoringoccasions) or based on configured HARQ processes for UE 115-a.

If ACK feedback 320 is based on configured HARQ processes for UE 115-a,base station 105-a may indicate ACK feedback 320 is to be transmittedfor all or a subset of the configured HARQ processes for UE 115-a. EachHARQ process may include a corresponding code block group/transportblock level ACK bits based on its configuration. In some cases, UE 115-amay be explicitly triggered by ACK trigger 315 for ACK feedback 320along with an indication of a particular TTI (e.g., slot, symbol, etc.)for transmitting ACK feedback 320. Additionally, an ACK delay may beindicated in a downlink grant (e.g., embedded in ACK trigger 315 or by aseparate DCI). While the ACK delay in the downlink grant may notimplicitly trigger ACK feedback 320, it may determine how UE 115-apopulates fields for ACK feedback 320. For example, UE 115-a maydetermine an ACK ready time based on the ACK delay and the downlinkgrant (e.g., a PDSCH transmission) for each HARQ process. Accordingly,if the ACK ready time occurs before UE 115-a receives ACK trigger 315(or is similarly triggered), UE 115-a may populate the fields for ACKfeedback 320 based on decoding results for the corresponding HARQprocess (e.g., ACK if successfully decoded, NACK if unsuccessfullyreceived/decoded). Alternatively, if the ACK ready time extends past thetime UE 115-a is triggered for ACK feedback 320, UE 115-a may populatethe corresponding fields for ACK feedback 320 with previous values forthe HARQ process or with a default value (e.g., ACK or NACK). Basestation 105-a may accordingly interpret if the fields for each HARQprocess are based on decoding results, previous values, or defaultvalues by comparing the ACK delay for each HARQ process with thetimeline that ACK feedback 320 was received.

Alternatively, if ACK feedback 320 is based on downlink channelmonitoring occasion(s), base station 105-a may further indicate a numberof downlink channel monitoring occasion(s) for which UE 115-a transmitsACK feedback 320. In some cases, the downlink channel monitoringoccasion(s) may be based on time locations for ACK feedback 320.Additionally, the downlink channel monitoring occasions may extendacross one or more TxOps, such that ACK feedback for downlink messagesin a first TxOp that UE 115-a was not able to process completely may betransmitted in ACK feedback 320 of a subsequent TxOp. As such, UE 115-amay skip gaps between the two TxOps for the ACK feedback where basestation 105-a does not have access to the unlicensed spectrum. In orderto transmit the ACK feedback for the first TxOp in the subsequent TxOP,UE 115-a may receive an indication on the start of the subsequent TxOpand/or at the end of the previous TxOP to determine the downlink channelmonitoring occasions of the corresponding TxOp.

In some cases, UE 115-a may determine a HARQ ACK codebook size fortransmitting ACK feedback 320 based on a number of downlink channelmonitoring occasions and/or a configured HARQ processes. For example,base station 105-a may trigger UE 115-a to send ACK feedback 320 basedon downlink channel monitoring occasions in some instances.Alternatively, in some other instances, base station 105-a may triggerUE 115-a to send ACK feedback 320 based on the configured HARQprocesses. Additionally, base station 105-a may further indicate whichACK feedback (e.g., based on the downlink channel monitoring occasionsor based on the configured HARQ processes) is used within the trigger.Additionally or alternatively, communications between base station 105-aand UE 115-a may include multiple channels (e.g., on one or moresubbands of carriers 305 and/or 310), and the HARQ ACK codebook size maybe further based on the number of channels or a number of indicatedchannels (e.g., active channels, subset of active channels, or checkedout channels). Base station 105-a may transmit the indicated channelsembedded in a downlink grant, included in a trigger downlink controlinformation, included in a common PDCCH, included in a layer 1 (L1)channel, or included in a preamble, where UE 115-a transmits the ACKfeedback for the indicated channels.

FIG. 4 illustrates an example of an ACK feedback schedule 400 thatsupports ACK feedback in unlicensed NR in accordance with variousaspects of the present disclosure. In some examples, ACK feedbackschedule 400 may implement aspects of wireless communications systems100 and/or 300. ACK feedback schedule 400 may include downlink anduplink transmissions between a base station 105 and a UE 115 for HARQACK feedback, where the base station 105 and UE 115 are examples ofcorresponding devices as described with reference to FIGS. 1-3. Asdescribed herein, ACK feedback schedule 400 may further include ACKfeedback transmitted according to a HARQ ACK codebook size based on, forexample, a number of configured HARQ processes for the UE 115.

The base station 105 and UE 115 may first transmit one or more downlinkand uplink messages in a preparation stage 405 to establish a connectionbetween the two wireless devices (e.g., random access channel (RACH)messaging, RRC configurations, etc.). The base station 105 and UE 115may then enter a data transmission stage 410, which includes a set ofdownlink transmissions 415 and an uplink transmission 420, where datatransmission stage 410 includes a number of TTIs 425 (e.g., slots). Theset of downlink transmissions 415 may include one or more downlinkmessages (e.g., DCI, PDCCH, downlink grants, PDSCH, etc.), and the UE115 may transmit ACK feedback in the uplink transmission 420 for the oneor more of downlink messages according to the HARQ ACK codebook sizebased on the number of configured HARQ processes. In some cases, the UE115 may transmit a block ACK feedback in situations such as in responseto the set of downlink transmissions 415 from the base station 105.Accordingly, the base station 105 may reduce feedback overhead from theUE 115 by triggering the UE 115 to transmit the ACK feedback for allconfigured HARQ processes once during a TxOp, and after the set ofdownlink transmissions 415 are finished within the TxOp.

For example, the HARQ ACK codebook size may be based on 16 configuredHARQ processes for the UE 115 (e.g., HARQ0 to HARQ15). As such, when thebase station 105 triggers the UE 115 to send the ACK feedback after theset of downlink transmissions 415 are finished, the UE 115 may send ACKfeedback for all 16 HARQ processes, where the first field of the HARQACK codebook indicates ACK feedback for HARQ0 and the last fieldindicates ACK feedback for HARQ15. The size of each field may depend ona configuration from the base station 105. If the UE 115 does not detectany data for a particular HARQ process, the UE 115 may populate thecorresponding field with a default value, previous value determined forthe HARQ process, etc. In some cases, the base station 105 may indicatefor the UE 115 to transmit the ACK feedback more frequently (e.g., ineach TTI 425).

FIG. 5 illustrates an example of an ACK feedback schedule 500 thatsupports ACK feedback in unlicensed NR in accordance with variousaspects of the present disclosure. In some examples, ACK feedbackschedule 500 may implement aspects of wireless communications systems100 and/or 300. ACK feedback schedule 500 may include downlink anduplink transmissions between a base station 105 and a UE 115 for HARQACK feedback, where the base station 105 and UE 115 are examples ofcorresponding devices as described with reference to FIGS. 1-4. Asdescribed herein, similar to ACK feedback schedule 400, ACK feedbackschedule 500 may further include ACK feedback transmitted according to aHARQ ACK codebook size based on, for example, a number of configuredHARQ processes for the UE 115.

Alternatively to transmitting the ACK feedback once per a TxOp (e.g.,after a set of downlink transmissions are finished within the TxOp), theUE 115 may receive a trigger (e.g., in a separate DCI or embedded in adownlink grant) to transmit ACK feedback for one or more downlinkmessages 515 in uplink messages 520 within a corresponding TTI 525(e.g., a slot). For example, within TTI 525-a, the UE 115 may receive atrigger in downlink message 515-a and transmit ACK feedback for allconfigured HARQ processes in uplink message 520-a. Data transmissionstage 510 of the TxOp may include a number of TTIs 525 up to TTI 525-nwith a corresponding downlink message 515-n and uplink message 520-n.Accordingly, within each TTI 525, if a trigger is not received in adownlink control portion associated with the corresponding downlinkmessage 515, the UE 115 may not transmit ACK feedback for the configuredHARQ processes in the corresponding uplink message 520. More frequentACK feedback may allow faster outer loop adaptation for better linkefficiency between the UE 115 and the base station 105.

As described herein, the base station 105 may configure the UE 115 witha number of HARQ processes (e.g., 16 processes or less), where the UE115 reports ACK feedback for each HARQ process such that the HARQ ACKcodebook size is based on the number of configured HARQ processes. Assuch, each time the base station 105 triggers the UE 115 to transmit theACK feedback (e.g., in every TTI 525 as described with reference to FIG.5), the UE 115 may report the corresponding ACK feedback for each HARQprocess determined up until the trigger in a sequential field order. Ifthe UE 115 does not detect any data for a particular HARQ process, theUE 115 may populate the corresponding field with a default value,previous value determined for the HARQ process, etc. In some cases,processing time for the ACK feedback may extend past the end of the TxOpsuch that default or previous values for one or more of the HARQprocesses may be transmitted rather than values based on decodingresults.

FIG. 6 illustrates an example of a downlink monitoring scheme 600 thatsupports ACK feedback in unlicensed NR in accordance with variousaspects of the present disclosure. In some examples, downlink monitoringscheme 600 may implement aspects of wireless communications systems 100and/or 300. Downlink monitoring scheme 600 may include downlink anduplink transmissions between a base station 105 and a UE 115 for HARQACK feedback, where the base station 105 and UE 115 are examples ofcorresponding devices as described with reference to FIGS. 1-5. Asdescribed herein, downlink monitoring scheme 600 may further include ACKfeedback transmitted according to a HARQ ACK codebook size based on, forexample, downlink channel monitoring occasions. The downlink channelmonitoring occasions may be either downlink data channel monitoringoccasions or downlink control channel monitoring occasions.

The base station 105 and UE 115 may communicate across one or more TxOps605, where a span of no medium access may occur between the TxOps suchthat the base station 105 may not access resources of an unlicensedspectrum. Additionally, the base station 105 may configure one or moredownlink channel monitoring occasions 610 with a correspondingmonitoring occasion duration 615, where the UE 115 may transmit ACKfeedback in an uplink message 620 associated with downlink channelmonitoring occasion 610. For example, downlink channel monitoringoccasion 610-a may include control information for the UE 115 totransmit ACK feedback in uplink message 620-a for corresponding downlinkmessages 625 within monitoring occasion duration 615-a (e.g., downlinkmessages 625-a and 625-b). As shown, monitoring occasion duration 615-amay include two (2) slots, where the duration may be based on a maximumslot timing value of two (2) signaled by the base station 105 for the UE115. Accordingly, the UE 115 may determine the HARQ ACK codebook sizebased on the number of downlink channel monitoring occasions 610.

In some cases, the base station 105 may indicate to the UE 115 on thestart and/or end of a TxOp 605 to determine a number of downlink channelmonitoring occasions 610 for the HARQ ACK codebook size and to determinewhen the downlink channel monitoring occasions 610 start in each TxOp605 and where the previous TxOP ends. For example, the base station 105may include control information in downlink channel monitoring occasion610-b for the UE 115 to transmit ACK feedback in uplink message 620-bfor corresponding downlink messages 625 within monitoring occasionduration 615-b, where monitoring occasion duration 615-b spans multipledownlink messages 625 across TxOp 605-a and TxOp 605-b (e.g., downlinkmessages 625-c and 625-d). By knowing the start of TxOp 605-b and end ofTxOp 605-a, the UE 115 may detect downlink channel monitoring occasion610-b and transmit the ACK feedback for the corresponding downlinkmessages in both TxOps 605. As such, the UE 115 may additionallydetermine the HARQ ACK codebook size based on skipping the gap betweenTxOp 605-a and TxOp 605-b, where the base station 105 may not haveaccess to the unlicensed medium. That is, the UE 115 may monitor thedownlink control channel (e.g., PDCCH) during the gap, but the downlinkchannel monitoring occasions during the gap may not be included in theHARQ ACK codebook.

When transmitting the ACK feedback according to the HARQ ACK codebooksize for each downlink channel monitoring occasion 610, the UE 115 maytransmit an ACK feedback for each downlink message 625 associated withthe corresponding downlink channel monitoring occasion 610. For example,if the base station 105 triggers the UE 115 to transmit ACK feedback indownlink channel monitoring occasion 610-b, the UE 115 may include ACKfeedback for downlink channel monitoring occasion 610-a (e.g., includingdownlink message 625-a and downlink message 625-b) and for downlinkchannel monitoring occasion 610-b (e.g., including downlink message625-c and downlink message 625-d) according to the determined HARQ ACKcodebook. Additionally, in some cases, interference or issues stemmingfrom communicating in the unlicensed spectrum may result in the UE 115missing ACK transmissions corresponding to a downlink channel monitoringoccasion 610.

FIG. 7 illustrates an example of an adjusted ACK feedback schedule 700that supports ACK feedback in unlicensed NR in accordance with variousaspects of the present disclosure. In some examples, adjusted ACKfeedback schedule 700 may implement aspects of wireless communicationssystems 100 and/or 300. ACK feedback schedule 700 may include downlinkand uplink transmissions between a base station 105 and a UE 115 forHARQ ACK feedback, where the base station 105 and UE 115 are examples ofcorresponding devices as described with reference to FIGS. 1-6. Asdescribed herein, similar to downlink monitoring scheme 600, ACKfeedback schedule 700 may further include ACK feedback transmittedaccording to a HARQ ACK codebook size based on, for example, downlinkchannel monitoring occasions. The downlink channel monitoring occasionsmay be either downlink data channel monitoring occasions or downlinkcontrol channel monitoring occasions.

In some cases, the UE 115 may miss one or more ACK transmissions due tointerferences or issues stemming from communicating in an unlicensedspectrum (e.g., LBT issues). For example, the UE 115 may receive atrigger for ACK feedback in downlink channel monitoring occasions 710-aand/or 710-b, but may miss transmitting the ACK feedback incorresponding uplink messages 705-a (e.g., TTI n) and 705-b. The basestation 105 may detect the issue in a TTI after the first missed ACKfeedback (e.g., TTI n+1). Accordingly, the base station 105 may thenrequest an ACK feedback (e.g., by triggering the UE 115) in a downlinkchannel monitoring occasion 710-c in a subsequent TTI (e.g., TTI n+2),where downlink channel monitoring occasion 710-c includes controlinformation for the UE 115 to transmit ACK feedback for downlinkmessages that span a monitoring occasion duration 715-e in an uplinkmessage 720. As such uplink message 720 may include the missed ACKfeedback for the downlink messages associated with downlink channelmonitoring occasion 710-a and uplink message 705-a (e.g., downlinkmessages in monitoring occasion duration 715-b). For example, monitoringoccasion durations 715-a, 715-b, 715-c, and 715-d may span two (2) TTIs(e.g., slots) for corresponding downlink channel monitoring occasions,while monitoring occasion duration 715-e may span four (4) TTIs fordownlink channel monitoring occasion 710-c to include downlink messagesassociated with the missed ACK feedback in uplink message 705-a.

However, the base station 105 may request ACK feedback for a subset ofthe TTIs in monitoring occasion duration 715-e and may receive ACKfeedback for one of the slots while establishing the new monitoringoccasion duration 715 in response to the missed ACK feedbacktransmission. Accordingly, the specific set of downlink channelmonitoring occasions and corresponding downlink channels to transmit ACKfeedback for may be derived through higher layer signaling (e.g., RRCconfiguration) and DCI. For example, a table configured by the higherlayer signaling may indicate which downlink channel monitoringoccasion(s) to transmit the ACK feedback based on the originallyconfigured monitoring occasion duration 715 (e.g., TTI n if the originalmonitoring occasion duration 715 equaled one (1) TTI or TTIs n and n−1or TTIs n and n−2 if the original monitoring occasion duration 715equaled two (2) TTIs). DCI may then indicate one of the options ifmultiple options are present (e.g., by indicating the index or indicesof the TTIs). In some cases, the UE 115 may determine a new HARQ ACKcodebook size for the newly established monitoring occasion duration 715or may use the same HARQ ACK codebook size based on the number ofdownlink channel monitoring occasions. Note that this determination mayrequire an indication of the set of TTIs and/or number of TTIs toinclude in the HARQ feedback in the downlink DCI (e.g., downlink oruplink grant, ACK trigger, etc.). This requirement may enhance thesemi-static codebook size computation mode of NR. Further, as codebooksize is determined based on a number of TTIs indicated in the DCI, suchan indication may allow for a dynamic codebook size.

As described herein, the ACK feedback sent on an uplink message (e.g.,an uplink message 705) may include the ACK feedback for all slots withinthe codebook size determination window or may include ACK feedback for aparticular ACK resource (e.g., via an ACK resource indicator in a DCImessage). The HARQ ACK codebook size may still be based on all slotsthat are may be included within the codebook size determination window(which may include DCI that point to the ACK resources, other slots thatmay not have DCI detected, or slots that may have DCI pointed to anotherACK resource). The ACK feedback for slots that point to the ACK resourcemay be set per PDSCH decoding status, while ACK feedback for rest of theslots may be set to a fixed value such as in NACK. Additionally oralternatively, the HARQ feedback process may allow the UE 115 to switchbetween the above two methods of HARQ ACK feedback based on for example,an explicit indication in the DCI or an implicit indication based onsome other parameters in the DCI.

FIG. 8 illustrates an example of an ACK feedback scheme 800 thatsupports ACK feedback in unlicensed NR in accordance with variousaspects of the present disclosure. In some examples, ACK feedback scheme800 may implement aspects of wireless communications systems 100 and/or300. ACK feedback scheme 800 may include downlink and uplinktransmissions between a base station 105 and a UE 115 for HARQ ACKfeedback, where the base station 105 and UE 115 are examples ofcorresponding devices as described with reference to FIGS. 1-7. Asdescribed herein, ACK feedback scheme 800 may further include ACKfeedback transmitted according to a HARQ ACK codebook size based on, forexample, both a number of downlink channel monitoring occasions and anumber of configured HARQ processes for the UE 115. The downlink channelmonitoring occasions may be either downlink data channel monitoringoccasions or downlink control channel monitoring occasions.

Accordingly, the UE 115 may determine a HARQ ACK codebook size based onthe number of downlink channel monitoring occasions that can satisfyself-contained ACK feedback within a same TxOp 805. Additionally, thebase station 105 may trigger the UE 115 to transmit ACK feedback for thenumber of configured HARQ processes or a subset thereof. By additionallytriggering the UE 115 to transmit ACK feedback based on the configuredHARQ processes, downlink channel monitoring occasions not processedwithin the same TxOp 805 (and their ACK feedback) would spill over intoa subsequent TxOp 805 would be covered. The trigger for transmitting theACK feedback may be embedded in a downlink grant, uplink grant, or in aseparate trigger DCI. Additionally, the trigger may indicate the type ofACK feedback. For example, the trigger may indicate that the UE 115reports ACK feedback according to the most recent downlink channelmonitoring occasions (e.g., type 1 trigger). Alternatively, the triggermay indicate that the UE reports the ACK feedback for the triggered oneor more indicated HARQ processes (e.g., type 2 trigger).

In the example of ACK feedback scheme 800, the UE 115 may transmit ACKfeedback in one or more uplink messages 820 that correspond to downlinkchannel monitoring occasions 810 in TxOps 805. Downlink channelmonitoring occasion 810-a may indicate a monitoring occasion duration815-a for downlink messages (e.g., two (2) slots) for which the UE 115may transmit ACK feedback in uplink message 820-a. Alternatively,downlink channel monitoring occasion 810-b may indicate for the UE 115to transmit ACK feedback for the configured HARQ processes (or subsetthereof) in uplink message 820-b. Additionally, similar to downlinkchannel monitoring occasion 810-a, downlink channel monitoring occasion810-c may indicate a monitoring occasion duration 815-b for downlinkmessages (e.g., two (2) slots) for which the UE 115 may transmit ACKfeedback in uplink message 820-c.

Additionally or alternatively, as described herein, communicationsbetween the base station 105 and the UE 115 may include multiplechannels (e.g., on one or more subbands), and the HARQ ACK codebook sizemay be further based on the number of channels or a number of indicatedchannels (e.g., active channels, subset of active channels, or checkedout channels). The base station 105 may transmit the indicated channelsembedded in a downlink grant, uplink grant, included in a triggerdownlink control information, included in a common PDCCH, included in anL1 channel, or included in a preamble, where the UE 115 transmits theACK feedback for the indicated channels.

FIG. 9 illustrates an example of a process flow 900 that supports ACKfeedback in unlicensed NR in accordance with various aspects of thepresent disclosure. In some examples, process flow 900 may implementaspects of communications systems 100 and/or 300. Process flow 900 mayinclude a base station 105-b and a UE 115-b, which may be examples ofcorresponding devices as described with reference to FIGS. 1-8. Asdescribed herein, base station 105-b and UE 115-b may communicate in anunlicensed spectrum (e.g., shared radio frequency spectrum band).

In the following description of the process flow 900, the operationsbetween UE 115-b and base station 105-b may be performed in differentorders or at different times. Certain operations may also be left out ofthe process flow 900, or other operations may be added to the processflow 900. It is to be understood that while UE 115-b and base station105-b are shown performing a number of the operations of process flow900, any wireless device may perform the operations shown.

At 905, base station 105-b may transmit a feedback indication to UE115-b, where the feedback indication indicates to UE 115-b whether it isto determine a HARQ ACK codebook size based on a duration of a downlinkchannel monitoring occasion or a number of configured HARQ processes. Insome cases, base station 105-b may transmit the feedback indicationembedded in a downlink grant or in a separate trigger DCI.

At 910, UE 115-b may identify a duration of a downlink channelmonitoring occasion for which HARQ feedback is to be reported. In somecases, UE 115-b may receive, during a TxOp in which a downlink channelmonitoring occasion is to occur but before the downlink channelmonitoring occasion occurs, information from which UE 115-b is able todetermine the duration of the downlink channel monitoring occasion.Additionally or alternatively, UE 115-b may identify at least onedownlink channel monitoring occasion.

At 915, UE 115-b may receive a feedback trigger for transmission of HARQfeedback. In some cases, UE 115-b may receive the feedback trigger viaDCI or embedded in a downlink grant. Additionally or alternatively, UE115-b may receive a trigger for HARQ feedback for a set of configuredHARQ processes for UE 115-b. Accordingly, UE 115-b may receive aplurality of predefined sets of configured HARQ processes via RRCsignaling. In some cases, the feedback trigger may further indicatewhether a HARQ ACK codebook size determination may be based on theduration of the at least one downlink channel monitoring occasion or onthe number of configured HARQ processes.

At 920, UE 115-b may determine a HARQ ACK codebook size based on theduration of the downlink channel monitoring occasion. Additionally oralternatively, UE 115-b may determine the HARQ ACK codebook size basedon a number of configured HARQ processes. In some cases, UE 115-b maydetermine the HARQ ACK codebook size based on receiving, in DCI, anindication of a number of downlink channel monitoring occasions toinclude in determining the HARQ ACK codebook size. Additionally oralternatively, UE 115-b may determine the HARQ ACK codebook size basedon receiving, in DCI, an indication of a set of downlink channelmonitoring occasions to include in determining the HARQ ACK codebooksize, where the set is one of a plurality of predefined sets of downlinkchannel monitoring occasions. Accordingly, UE 115-b may receive theplurality of predefined sets of downlink channel monitoring occasionsvia RRC signaling.

In some cases, UE 115-b may determine the HARQ ACK codebook size basedon the duration of the downlink channel monitoring occasion for a firstset of HARQ feedback instances of the HARQ feedback and on a number ofconfigured HARQ processes for a second set of HARQ feedback instances ofthe HARQ feedback. In some cases, the first set of HARQ feedbackinstances may be transmitted during a same TxOp, and the second set ofHARQ feedback instances may be transmitted in a different TxOp.Additionally or alternatively, UE 115-b may determine the HARQ ACKcodebook size based on a total number of channels associated with theUE. In some cases, UE 115-b may receive a channel indication of a numberof channels to be included in determining the HARQ ACK codebook size(e.g., a number of checked out channels) and may determine the HARQ ACKcodebook size based on the number of channels indicated by the channelindication. Accordingly, UE 115-b may receive the channel indicationembedded in a downlink grant, included in a trigger DCI, included in anL1 channel, or included in a preamble. In some cases, the HARQ ACKcodebook size may encompass a number of TTIs. The number of TTIsencompassed by the HARQ ACK codebook size may span two different TxOps.Additionally or alternatively, at least some of the number of TTIs maybe non-contiguous.

At 925, UE 115-b may receive, in association with a downlink grant, anACK delay indication, where the ACK delay indication indicates a minimumtime by which HARQ feedback is to be delayed. In some cases, the ACKdelay may include N slots where N is based on a UE capability indicationfor UE 115-b. For example, when N=1, a downlink message (e.g., a PDSCHmessage) is sent on slot n and UE 115-b may generate ACK feedback inslot n+1.

At 930, UE 115-b may populate the HARQ feedback based on the ACK delayindication and receipt of a downlink channel. In some cases, UE 115-bmay populate the HARQ feedback using decoding results when an ACK readytime for the downlink channel is less than the ACK delay indication.Additionally or alternatively, UE 115-b may populate the HARQ feedbackusing default values when an ACK ready time for the downlink channel isgreater than the ACK delay indication. Accordingly, UE 115-b maypopulate the HARQ feedback using an ACK value, a negative ACK (NACK)value, or a previous ACK/NACK value.

At 935, UE 115-b may transmit, to base station 105-b, the HARQ feedbackin accordance with the HARQ ACK codebook size.

FIG. 10 shows a block diagram 1000 of a wireless device 1005 thatsupports acknowledgement (ACK) feedback in unlicensed NR in accordancewith aspects of the present disclosure. Wireless device 1005 may be anexample of aspects of a UE 115 as described herein. Wireless device 1005may include receiver 1010, UE communications manager 1015, andtransmitter 1020. Wireless device 1005 may also include a processor.Each of these components may be in communication with one another (e.g.,via one or more buses).

Receiver 1010 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, channels, and information related to ACK feedback inunlicensed NR, etc.). Information may be passed on to other componentsof the device. The receiver 1010 may be an example of aspects of thetransceiver 1335 described with reference to FIG. 13. The receiver 1010may utilize a single antenna or a set of antennas.

UE communications manager 1015 may be an example of aspects of the UEcommunications manager 1315 described with reference to FIG. 13.

UE communications manager 1015 and/or at least some of its varioussub-components may be implemented in hardware, software executed by aprocessor, firmware, or any combination thereof. If implemented insoftware executed by a processor, the functions of the UE communicationsmanager 1015 and/or at least some of its various sub-components may beexecuted by a general-purpose processor, a digital signal processor(DSP), an application-specific integrated circuit (ASIC), anfield-programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described in thepresent disclosure. The UE communications manager 1015 and/or at leastsome of its various sub-components may be physically located at variouspositions, including being distributed such that portions of functionsare implemented at different physical locations by one or more physicaldevices. In some examples, UE communications manager 1015 and/or atleast some of its various sub-components may be a separate and distinctcomponent in accordance with various aspects of the present disclosure.In other examples, UE communications manager 1015 and/or at least someof its various sub-components may be combined with one or more otherhardware components, including but not limited to an I/O component, atransceiver, a network server, another computing device, one or moreother components described in the present disclosure, or a combinationthereof in accordance with various aspects of the present disclosure.

UE communications manager 1015 may identify a duration of a downlinkchannel monitoring occasion (either a downlink data channel monitoringoccasion or a downlink control channel monitoring occasion) for whichHARQ feedback is to be reported. The UE communications manager 1015 maythen determine a HARQ ACK codebook size based on the duration of thedownlink channel monitoring occasion and transmit the HARQ feedback inaccordance with the HARQ ACK codebook size. Additionally oralternatively, the UE communications manager 1015 may identify at leastone downlink channel monitoring occasion. Accordingly, the UEcommunications manager 1015 may receive a feedback trigger fortransmission of HARQ feedback and determine a HARQ ACK codebook sizebased on a number of configured HARQ processes. The UE communicationsmanager 1015 may then transmit the HARQ feedback in accordance with theHARQ ACK codebook size.

Transmitter 1020 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1020 may be collocatedwith a receiver 1010 in a transceiver module. For example, thetransmitter 1020 may be an example of aspects of the transceiver 1335described with reference to FIG. 13. The transmitter 1020 may utilize asingle antenna or a set of antennas.

FIG. 11 shows a block diagram 1100 of a wireless device 1105 thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure. Wireless device 1105 may be an example of aspects ofa wireless device 1005 or a UE 115 as described with reference to FIG.10. Wireless device 1105 may include receiver 1110, UE communicationsmanager 1115, and transmitter 1120. Wireless device 1105 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses).

Receiver 1110 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, channels, and information related to ACK feedback inunlicensed NR, etc.). Information may be passed on to other componentsof the device. The receiver 1110 may be an example of aspects of thetransceiver 1335 described with reference to FIG. 13. The receiver 1110may utilize a single antenna or a set of antennas.

UE communications manager 1115 may be an example of aspects of the UEcommunications manager 1315 described with reference to FIG. 13.

UE communications manager 1115 may also include monitoring occasioncomponent 1125, codebook size component 1130, HARQ feedback component1135, and feedback trigger component 1140.

Monitoring occasion component 1125 may identify a duration of a downlinkchannel monitoring occasion for which HARQ feedback is to be reported.In some cases, monitoring occasion component 1125 may receive, during aTxOp in which a downlink channel monitoring occasion is to occur butbefore the downlink channel monitoring occasion occurs, information fromwhich the UE is able to determine the duration of the downlink channelmonitoring occasion. Additionally or alternatively, monitoring occasioncomponent 1125 may identify at least one downlink channel monitoringoccasion. The downlink channel monitoring occasion may be either adownlink data channel monitoring occasion or a downlink control channelmonitoring occasion.

Codebook size component 1130 may determine a HARQ ACK codebook sizebased on the duration of the downlink channel monitoring occasion. Insome cases, the HARQ ACK codebook size encompasses a number of TTIs. Insome cases, the number of TTIs encompassed by the HARQ ACK codebook sizespans two different TxOps. Additionally or alternatively, in some cases,at least some of the number of TTIs are non-contiguous.

HARQ feedback component 1135 may transmit the HARQ feedback inaccordance with the HARQ ACK codebook size.

Feedback trigger component 1140 may receive, at the UE, a feedbacktrigger for transmission of HARQ feedback. In some cases, codebook sizecomponent 1130 may then determine a HARQ ACK codebook size based on anumber of configured HARQ processes for the triggered HARQ feedback.Additionally, receiving the feedback trigger may include receiving thefeedback trigger via downlink control information or embedded in adownlink grant. Alternatively, in some cases, receiving the feedbacktrigger may include receiving a trigger for HARQ feedback for a set ofconfigured HARQ processes for the UE. Accordingly, feedback triggercomponent 1140 may receive a set of predefined sets of configured HARQprocesses via RRC signaling.

Transmitter 1120 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1120 may be collocatedwith a receiver 1110 in a transceiver module. For example, thetransmitter 1120 may be an example of aspects of the transceiver 1335described with reference to FIG. 13. The transmitter 1120 may utilize asingle antenna or a set of antennas.

FIG. 12 shows a block diagram 1200 of a UE communications manager 1215that supports ACK feedback in unlicensed NR in accordance with aspectsof the present disclosure. The UE communications manager 1215 may be anexample of aspects of a UE communications manager 1015, a UEcommunications manager 1115, or a UE communications manager 1315described with reference to FIGS. 10, 11, and 13. The UE communicationsmanager 1215 may include monitoring occasion component 1220, codebooksize component 1225, HARQ feedback component 1230, feedback triggercomponent 1235, monitoring occasion based size component 1240, combinedfeedback component 1245, combined feedback trigger component 1250,multi-channel based size component 1255, and ACK delay component 1260.Each of these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

Monitoring occasion component 1220 may identify a duration of a downlinkchannel monitoring occasion to report HARQ feedback. In some cases,monitoring occasion component 1220 may receive, during a TxOp in which adownlink channel monitoring occasion is to occur but before the downlinkchannel monitoring occasion occurs, information from which the UE isable to determine the duration of the downlink channel monitoringoccasion. Additionally or alternatively, monitoring occasion component1220 may identify at least one downlink channel monitoring occasion. Thedownlink channel monitoring occasion may be either a downlink datachannel monitoring occasion or a downlink control channel monitoringoccasion.

Codebook size component 1225 may determine a HARQ ACK codebook sizebased on the duration of the downlink channel monitoring occasion. Insome cases, the HARQ ACK codebook size encompasses a number of TTIs. Insome cases, the number of TTIs encompassed by the HARQ ACK codebook sizespans two different TxOps. Additionally or alternatively, in some cases,at least some of the number of TTIs are non-contiguous.

HARQ feedback component 1230 may transmit the HARQ feedback inaccordance with the HARQ ACK codebook size.

Feedback trigger component 1235 may receive, at the UE, a feedbacktrigger for transmission of HARQ feedback. In some cases, codebook sizecomponent 1225 may then determine a HARQ ACK codebook size based on anumber of configured HARQ processes for the triggered HARQ feedback.Additionally, receiving the feedback trigger may include receiving thefeedback trigger via downlink control information or embedded in adownlink grant. Alternatively, in some cases, receiving the feedbacktrigger may include receiving a trigger for HARQ feedback for a set ofconfigured HARQ processes for the UE. Accordingly, feedback triggercomponent 1235 may receive a set of predefined sets of configured HARQprocesses via RRC signaling.

Monitoring occasion based size component 1240 may receive, in downlinkcontrol information, an indication of a number of downlink channelmonitoring occasions to include in determining the HARQ ACK codebooksize. Additionally or alternatively, monitoring occasion based sizecomponent 1240 may receive, in downlink control information, anindication of a set of downlink channel monitoring occasions to includein determining the HARQ ACK codebook size, where the set is one of a setof predefined sets of downlink channel monitoring occasions. In somecases, monitoring occasion based size component 1240 may receive the setof predefined sets of downlink channel monitoring occasions via RRCsignaling.

Combined feedback component 1245 may determine the HARQ ACK codebooksize based on the duration of the downlink channel monitoring occasionfor a first set of HARQ feedback instances of the HARQ feedback andbased on a number of configured HARQ processes for a second set of HARQfeedback instances of the HARQ feedback. In some cases, the first set ofHARQ feedback instances may be transmitted during a same TxOp, and thesecond set of HARQ feedback instances may be transmitted in a differentTxOp.

Combined feedback trigger component 1250 may receive a feedback triggerindicating whether the HARQ ACK codebook size determination is to bebased on the duration of the at least one downlink channel monitoringoccasion or on the number of configured HARQ processes. In some cases,receiving the feedback trigger may include receiving the feedbacktrigger embedded in a downlink grant or in a separate trigger DCI.

Multi-channel based size component 1255 may determine the HARQ ACKcodebook size based on the number of channels indicated by the channelindication. In some cases, multi-channel based size component 1255 mayfurther determine the HARQ ACK codebook size based on a total number ofchannels associated with the UE. Additionally or alternatively,multi-channel based size component 1255 may receive a channel indicationof a number of channels to include for determining the HARQ ACK codebooksize. In some cases, receiving the channel indication may includereceiving the channel indication embedded in a downlink grant, includedin a trigger downlink control information, included in an L1 channel, orincluded in a preamble.

ACK delay component 1260 may receive, in association with a downlinkgrant, an ACK delay indication, where the ACK delay indication indicatesa minimum time by which HARQ feedback is to be delayed. Accordingly, ACKdelay component 1260 may populate the HARQ feedback based on the ACKdelay indication and receipt of a downlink channel. In some cases,populating the HARQ feedback may include populating the HARQ feedbackusing decoding results when an ACK ready time for the downlink channelis less than the ACK delay indication. Additionally or alternatively,populating the HARQ feedback may include populating the HARQ feedbackusing default values when an ACK ready time for the downlink channel isgreater than the ACK delay indication. Accordingly, populating the HARQfeedback with default values may include populating the HARQ feedbackusing an ACK value, a NACK value, or a previous ACK/NACK value.

FIG. 13 shows a diagram of a system 1300 including a device 1305 thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure. Device 1305 may be an example of or include thecomponents of wireless device 1005, wireless device 1105, or a UE 115 asdescribed herein, e.g., with reference to FIGS. 10 and 11. Device 1305may include components for bi-directional voice and data communicationsincluding components for transmitting and receiving communications,including UE communications manager 1315, processor 1320, memory 1325,software 1330, transceiver 1335, antenna 1340, and I/O controller 1345.These components may be in electronic communication via one or morebuses (e.g., bus 1310). Device 1305 may communicate wirelessly with oneor more base stations 105.

Processor 1320 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a central processing unit (CPU), amicrocontroller, an ASIC, an FPGA, a programmable logic device, adiscrete gate or transistor logic component, a discrete hardwarecomponent, or any combination thereof). In some cases, processor 1320may be configured to operate a memory array using a memory controller.In other cases, a memory controller may be integrated into processor1320. Processor 1320 may be configured to execute computer-readableinstructions stored in a memory to perform various functions (e.g.,functions or tasks supporting ACK feedback in unlicensed NR).

Memory 1325 may include random access memory (RAM) and read only memory(ROM). The memory 1325 may store computer-readable, computer-executablesoftware 1330 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 1325 may contain, among other things, a basic input/outputsystem (BIOS) which may control basic hardware or software operationsuch as the interaction with peripheral components or devices.

Software 1330 may include code to implement aspects of the presentdisclosure, including code to support ACK feedback in unlicensed NR.Software 1330 may be stored in a non-transitory computer-readable mediumsuch as system memory or other memory. In some cases, the software 1330may not be directly executable by the processor but may cause a computer(e.g., when compiled and executed) to perform functions describedherein.

Transceiver 1335 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 1335 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1335 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1340.However, in some cases the device may have more than one antenna 1340,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

I/O controller 1345 may manage input and output signals for device 1305.I/O controller 1345 may also manage peripherals not integrated intodevice 1305. In some cases, I/O controller 1345 may represent a physicalconnection or port to an external peripheral. In some cases, I/Ocontroller 1345 may utilize an operating system such as iOS®, ANDROID®,MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operatingsystem. In other cases, I/O controller 1345 may represent or interactwith a modem, a keyboard, a mouse, a touchscreen, or a similar device.In some cases, I/O controller 1345 may be implemented as part of aprocessor. In some cases, a user may interact with device 1305 via I/Ocontroller 1345 or via hardware components controlled by I/O controller1345.

FIG. 14 shows a block diagram 1400 of a wireless device 1405 thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure. Wireless device 1405 may be an example of aspects ofa base station 105 as described herein. Wireless device 1405 may includereceiver 1410, base station communications manager 1415, and transmitter1420. Wireless device 1405 may also include a processor. Each of thesecomponents may be in communication with one another (e.g., via one ormore buses).

Receiver 1410 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, channels, and information related to ACK feedback inunlicensed NR, etc.). Information may be passed on to other componentsof the device. The receiver 1410 may be an example of aspects of thetransceiver 1735 described with reference to FIG. 17. The receiver 1410may utilize a single antenna or a set of antennas.

Base station communications manager 1415 may be an example of aspects ofthe base station communications manager 1715 described with reference toFIG. 17.

Base station communications manager 1415 and/or at least some of itsvarious sub-components may be implemented in hardware, software executedby a processor, firmware, or any combination thereof. If implemented insoftware executed by a processor, the functions of the base stationcommunications manager 1415 and/or at least some of its varioussub-components may be executed by a general-purpose processor, a DSP, anASIC, an FPGA or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described in the presentdisclosure. The base station communications manager 1415 and/or at leastsome of its various sub-components may be physically located at variouspositions, including being distributed such that portions of functionsare implemented at different physical locations by one or more physicaldevices. In some examples, base station communications manager 1415and/or at least some of its various sub-components may be a separate anddistinct component in accordance with various aspects of the presentdisclosure. In other examples, base station communications manager 1415and/or at least some of its various sub-components may be combined withone or more other hardware components, including but not limited to anI/O component, a transceiver, a network server, another computingdevice, one or more other components described in the presentdisclosure, or a combination thereof in accordance with various aspectsof the present disclosure.

Base station communications manager 1415 may transmit a feedbackindication to a UE, where the feedback indication indicates to the UEwhether the UE is to determine a HARQ ACK codebook size based on aduration of a downlink channel monitoring occasion or a number ofconfigured HARQ processes. Accordingly, base station communicationsmanager 1415 may receive HARQ feedback in accordance with the HARQ ACKcodebook size and the feedback indication.

Transmitter 1420 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1420 may be collocatedwith a receiver 1410 in a transceiver module. For example, thetransmitter 1420 may be an example of aspects of the transceiver 1735described with reference to FIG. 17. The transmitter 1420 may utilize asingle antenna or a set of antennas.

FIG. 15 shows a block diagram 1500 of a wireless device 1505 thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure. Wireless device 1505 may be an example of aspects ofa wireless device 1405 or a base station 105 as described with referenceto FIG. 14. Wireless device 1505 may include receiver 1510, base stationcommunications manager 1515, and transmitter 1520. Wireless device 1505may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 1510 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, channels, and information related to ACK feedback inunlicensed NR, etc.). Information may be passed on to other componentsof the device. The receiver 1510 may be an example of aspects of thetransceiver 1735 described with reference to FIG. 17. The receiver 1510may utilize a single antenna or a set of antennas.

Base station communications manager 1515 may be an example of aspects ofthe base station communications manager 1715 described with reference toFIG. 17.

Base station communications manager 1515 may also include feedbackindication component 1525 and HARQ feedback receiver 1530.

Feedback indication component 1525 may transmit a feedback indication toa UE, where the feedback indication indicates to the UE whether the UEis to determine a HARQ ACK codebook size based on a duration of adownlink channel monitoring occasion or a number of configured HARQprocesses. In some cases, feedback indication component 1525 maytransmit the feedback indication embedded in a downlink grant or in aseparate trigger downlink control information.

HARQ feedback receiver 1530 may receive HARQ feedback in accordance withthe HARQ ACK codebook size and the feedback indication.

Transmitter 1520 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1520 may be collocatedwith a receiver 1510 in a transceiver module. For example, thetransmitter 1520 may be an example of aspects of the transceiver 1735described with reference to FIG. 17. The transmitter 1520 may utilize asingle antenna or a set of antennas.

FIG. 16 shows a block diagram 1600 of a base station communicationsmanager 1615 that supports ACK feedback in unlicensed NR in accordancewith aspects of the present disclosure. The base station communicationsmanager 1615 may be an example of aspects of a base stationcommunications manager 1715 described with reference to FIGS. 14, 15,and 17. The base station communications manager 1615 may includefeedback indication component 1620, HARQ feedback receiver 1625,monitoring occasion indicator 1630, and multi-channel indicator 1635.Each of these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

Feedback indication component 1620 may transmit a feedback indication toa UE, where the feedback indication indicates to the UE whether the UEis to determine a HARQ ACK codebook size based on a duration of adownlink channel monitoring occasion or a number of configured HARQprocesses. In some cases, feedback indication component 1620 maytransmit the feedback indication embedded in a downlink grant or in aseparate trigger downlink control information.

HARQ feedback receiver 1625 may receive HARQ feedback in accordance withthe HARQ ACK codebook size and the feedback indication.

Monitoring occasion indicator 1630 may transmit, in downlink controlinformation, an indication of a number of downlink channel monitoringoccasions to include in determining the HARQ ACK codebook size.Additionally or alternatively, monitoring occasion indicator 1630 maytransmit, in downlink control information, an indication of a set ofdownlink channel monitoring occasions to include in determining the HARQACK codebook size, where the set is one of a set of predefined sets ofdownlink channel monitoring occasions. In some cases, monitoringoccasion indicator 1630 may transmit the set of predefined sets ofdownlink channel monitoring occasions via RRC signaling.

Multi-channel indicator 1635 may transmit a channel indication of anumber of channels to be included in determining the HARQ ACK codebooksize (e.g., a number of checked out channels). In some cases,transmitting the channel indication may include transmitting the channelindication embedded in a downlink grant, included in a trigger downlinkcontrol information, included in an L1 channel, or included in apreamble.

FIG. 17 shows a diagram of a system 1700 including a device 1705 thatsupports ACK feedback in unlicensed NR in accordance with aspects of thepresent disclosure. Device 1705 may be an example of or include thecomponents of base station 105 as described herein, e.g., with referenceto FIG. 1. Device 1705 may include components for bi-directional voiceand data communications including components for transmitting andreceiving communications, including base station communications manager1715, processor 1720, memory 1725, software 1730, transceiver 1735,antenna 1740, network communications manager 1745, and inter-stationcommunications manager 1750. These components may be in electroniccommunication via one or more buses (e.g., bus 1710). Device 1705 maycommunicate wirelessly with one or more UEs 115.

Processor 1720 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, processor 1720 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into processor 1720. Processor 1720 may be configured toexecute computer-readable instructions stored in a memory to performvarious functions (e.g., functions or tasks supporting ACK feedback inunlicensed NR).

Memory 1725 may include RAM and ROM. The memory 1725 may storecomputer-readable, computer-executable software 1730 includinginstructions that, when executed, cause the processor to perform variousfunctions described herein. In some cases, the memory 1725 may contain,among other things, a BIOS which may control basic hardware or softwareoperation such as the interaction with peripheral components or devices.

Software 1730 may include code to implement aspects of the presentdisclosure, including code to support ACK feedback in unlicensed NR.Software 1730 may be stored in a non-transitory computer-readable mediumsuch as system memory or other memory. In some cases, the software 1730may not be directly executable by the processor but may cause a computer(e.g., when compiled and executed) to perform functions describedherein.

Transceiver 1735 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 1735 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1735 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1740.However, in some cases the device may have more than one antenna 1740,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

Network communications manager 1745 may manage communications with thecore network (e.g., via one or more wired backhaul links). For example,the network communications manager 1745 may manage the transfer of datacommunications for client devices, such as one or more UEs 115.

Inter-station communications manager 1750 may manage communications withother base station 105, and may include a controller or scheduler forcontrolling communications with UEs 115 in cooperation with other basestations 105. For example, the inter-station communications manager 1750may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, inter-station communications manager1750 may provide an X2 interface within an Long Term Evolution(LTE)/LTE-A wireless communication network technology to providecommunication between base stations 105.

FIG. 18 shows a flowchart illustrating a method 1800 for ACK feedback inunlicensed NR in accordance with aspects of the present disclosure. Theoperations of method 1800 may be implemented by a UE 115 or itscomponents as described herein. For example, the operations of method1800 may be performed by a UE communications manager as described withreference to FIGS. 10 through 13. In some examples, a UE 115 may executea set of codes to control the functional elements of the device toperform the functions described herein. Additionally or alternatively,the UE 115 may perform aspects of the functions described herein usingspecial-purpose hardware.

At 1805 the UE 115 may identify a duration of a downlink channelmonitoring occasion for which HARQ feedback is to be reported. Theoperations of 1805 may be performed according to the methods describedherein. In certain examples, aspects of the operations of 1805 may beperformed by a monitoring occasion component as described with referenceto FIGS. 10 through 13.

At 1810 the UE 115 may determine a HARQ ACK codebook size based on theduration of the downlink channel monitoring occasion. The operations of1810 may be performed according to the methods described herein. Incertain examples, aspects of the operations of 1810 may be performed bya codebook size component as described with reference to FIGS. 10through 13.

At 1815 the UE 115 may transmit the HARQ feedback in accordance with theHARQ ACK codebook size. The operations of 1815 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of 1815 may be performed by a HARQ feedback componentas described with reference to FIGS. 10 through 13.

FIG. 19 shows a flowchart illustrating a method 1900 for ACK feedback inunlicensed NR in accordance with aspects of the present disclosure. Theoperations of method 1900 may be implemented by a UE 115 or itscomponents as described herein. For example, the operations of method1900 may be performed by a UE communications manager as described withreference to FIGS. 10 through 13. In some examples, a UE 115 may executea set of codes to control the functional elements of the device toperform the functions described herein. Additionally or alternatively,the UE 115 may perform aspects of the functions described herein usingspecial-purpose hardware.

At 1905 the UE 115 may identify at least one downlink channel monitoringoccasion. The operations of 1905 may be performed according to themethods described herein. In certain examples, aspects of the operationsof 1905 may be performed by a monitoring occasion component as describedwith reference to FIGS. 10 through 13.

At 1910 the UE 115 may receive a feedback trigger for transmission ofHARQ feedback. The operations of 1910 may be performed according to themethods described herein. In certain examples, aspects of the operationsof 1910 may be performed by a feedback trigger component as describedwith reference to FIGS. 10 through 13.

At 1915 the UE 115 may determine a HARQ ACK codebook size based on anumber of configured HARQ processes. The operations of 1915 may beperformed according to the methods described herein. In certainexamples, aspects of the operations of 1915 may be performed by acodebook size component as described with reference to FIGS. 10 through13.

At 1920 the UE 115 may transmit the HARQ feedback in accordance with theHARQ ACK codebook size. The operations of 1920 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of 1920 may be performed by a HARQ feedback componentas described with reference to FIGS. 10 through 13.

FIG. 20 shows a flowchart illustrating a method 2000 for ACK feedback inunlicensed NR in accordance with aspects of the present disclosure. Theoperations of method 2000 may be implemented by a base station 105 orits components as described herein. For example, the operations ofmethod 2000 may be performed by a base station communications manager asdescribed with reference to FIGS. 14 through 17. In some examples, abase station 105 may execute a set of codes to control the functionalelements of the device to perform the functions described herein.Additionally or alternatively, the base station 105 may perform aspectsof the functions described herein using special-purpose hardware.

At 2005 the base station 105 may transmit a feedback indication to a UE,where the feedback indication indicates to the UE whether the UE is todetermine a HARQ ACK codebook size based on a duration of a downlinkchannel monitoring occasion or a number of configured HARQ processes.The operations of 2005 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations of 2005may be performed by a feedback indication component as described withreference to FIGS. 14 through 17.

At 2010 the base station 105 may receive HARQ feedback in accordancewith the HARQ ACK codebook size and the feedback indication. Theoperations of 2010 may be performed according to the methods describedherein. In certain examples, aspects of the operations of 2010 may beperformed by a HARQ feedback receiver as described with reference toFIGS. 14 through 17.

It should be noted that the methods described herein describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned herein as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEs115 with service subscriptions with the network provider. A small cellmay be associated with a lower-powered base station 105, as comparedwith a macro cell, and a small cell may operate in the same or different(e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Smallcells may include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs 115 with servicesubscriptions with the network provider. A femto cell may also cover asmall geographic area (e.g., a home) and may provide restricted accessby UEs 115 having an association with the femto cell (e.g., UEs 115 in aclosed subscriber group (CSG), UEs 115 for users in the home, and thelike). An eNB for a macro cell may be referred to as a macro eNB. An eNBfor a small cell may be referred to as a small cell eNB, a pico eNB, afemto eNB, or a home eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells, and may also support communicationsusing one or multiple component carriers.

The wireless communications system 100 or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations 105 may have similar frame timing, andtransmissions from different base stations 105 may be approximatelyaligned in time. For asynchronous operation, the base stations 105 mayhave different frame timing, and transmissions from different basestations 105 may not be aligned in time. The techniques described hereinmay be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA) or other programmable logic device (PLD), discretegate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable read only memory (EEPROM), flash memory, compactdisk (CD) ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other non-transitory medium thatcan be used to carry or store desired program code means in the form ofinstructions or data structures and that can be accessed by ageneral-purpose or special-purpose computer, or a general-purpose orspecial-purpose processor. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. Disk and disc, as used herein, include CD, laserdisc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveare also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication at a userequipment (UE) in a shared radio frequency spectrum band, comprising:identifying at least one downlink channel monitoring occasion;receiving, at the UE, a feedback trigger for transmission of hybridautomatic repeat request (HARQ) feedback, wherein the HARQ feedbacktrigger is embedded in a downlink control information, DCI, that isseparate from a grant for a downlink channel and wherein the HARQfeedback trigger is jointly coded with a ACK delay indication;determining a HARQ acknowledgement (ACK) codebook size based at least inpart on a number of configured HARQ processes, on the downlink channelmonitoring occasions, or a combination thereof; and transmitting theHARQ feedback in accordance with the HARQ ACK codebook size and the ACKdelay indication.
 2. The method of claim 1, further comprising:populating the HARQ feedback based at least in part on the ACK delayindication and receipt of the downlink channel.
 3. The method of claim2, wherein populating the HARQ feedback comprises: populating the HARQfeedback using decoding results when an ACK ready time for the downlinkchannel before reception of the feedback trigger, wherein the ACK readytime is a function of the ACK delay indication and the receipt of thedownlink channel.
 4. The method of claim 2, wherein populating the HARQfeedback comprises: populating the HARQ feedback using default valueswhen an ACK ready time for the downlink channel is greater than an ACKtransmission time.
 5. The method of claim 2, wherein populating the HARQfeedback with default values comprises: populating the HARQ feedbackusing an ACK value, a negative ACK (NACK) value, or a previous ACK/NACKvalue.
 6. The method of claim 1, further comprising: identifying aduration for the HARQ feedback to be reported; identifying a subset ofdownlink channel monitoring occasions within the duration for the HARQfeedback to be reported; and determining the HARQ ACK codebook sizebased at least in part on the number of downlink channel monitoringoccasions in the subset.
 7. The method of claim 6, wherein a controlmessage received in downlink control information indicates whether thesubset of downlink channel monitoring occasions comprises an ACKtransmission time, whether the subset comprises different channelmonitoring occasions, or a combination thereof.
 8. The method of claim7, wherein the ACK transmission time comprises a sum of datatransmission time and an ACK delay value corresponding to the ACK delayindication.
 9. The method of claim 7, wherein the message comprises anexplicit indication received in downlink control information.
 10. Themethod of claim 7, wherein the message comprises an implicit indicationbased at least in part on comparing a HARQ feedback parameter conveyedin downlink control information with a parameter conveyed in radioresource control.
 11. The method of claim 6, wherein a duration of thedownlink channel monitoring occasion is based at least in part on:receiving, during a transmission opportunity (TxOp) in which a downlinkchannel monitoring occasion is to occur but before the downlink channelmonitoring occasion occurs, information from which the UE is able todetermine the duration of the downlink channel monitoring occasion. 12.The method of claim 6, wherein determining the HARQ ACK codebook sizecomprises: receiving, in downlink control information, an indication ofthe number of downlink channel monitoring occasions to include indetermining the HARQ ACK codebook size.
 13. The method of claim 6,wherein determining the HARQ ACK codebook size comprises: receiving, indownlink control information, an indication of a set of downlink channelmonitoring occasions to include in determining the HARQ ACK codebooksize, wherein the set is one of a plurality of predefined sets ofdownlink channel monitoring occasions.
 14. The method of claim 13,further comprising: receiving the plurality of predefined sets ofdownlink channel monitoring occasions via radio resource control (RRC)signaling.
 15. The method of claim 6, wherein the HARQ ACK codebook sizeencompasses a number of transmission time intervals (TTIs), wherein atleast some of the number of TTIs are non-contiguous.
 16. The method ofclaim 15, wherein the number of TTIs encompassed by the HARQ ACKcodebook size spans two different transmission opportunities (TxOps).17. The method of claim 6, further comprising: determining the HARQ ACKcodebook size based at least in part on the duration of the downlinkchannel monitoring occasion for a first set of HARQ feedback instancesof the HARQ feedback; and determining the HARQ ACK codebook size basedat least in part on a number of configured HARQ processes for a secondset of HARQ feedback instances of the HARQ feedback.
 18. The method ofclaim 17, further comprising: receiving a feedback trigger thatindicates whether the HARQ ACK codebook size determination is to bebased on the duration of the at least one downlink channel monitoringoccasion or on the number of configured HARQ processes.
 19. The methodof claim 6, wherein the number of downlink channel monitoring occasionsare identified based at least in part on a time location of the HARQfeedback.
 20. The method of claim 6, wherein receiving the feedbacktrigger comprises: receiving a trigger for HARQ feedback in DCI for allof the configured HARQ processes or a subset of the configured HARQprocesses for the UE via radio resource control (RRC) signaling.
 21. Themethod of claim 20, wherein the subset of the configured HARQ processescomprises a bitmap indication with each bit in the bitmap correspondingto one HARQ process or a group of HARQ processes.